Autoscale with Edera zone metrics

3 min read · Intermediate

Developer Platform Engineer

Edera exposes per-pod zone metrics at http://<node-ip>:3035/metrics/kubernetes. Because pods run inside zones, these metrics are not available through cAdvisor or the kubelet. Prometheus must scrape the Edera endpoint directly.

Prerequisites

  • Prometheus installed in your cluster
  • Prometheus Adapter installed in your cluster
  • Edera running on each node and listening on port 3035

Available metrics

Edera exposes per-pod zone metrics labeled with namespace, pod, and zone_id. For the full list, see the Edera metrics reference.

1. Scrape the Edera daemon

Add a scrape job to Prometheus using additionalScrapeConfigs. The job uses Kubernetes node service discovery to find nodes automatically, then rewrites the address to target port 3035.

apiVersion: v1
kind: Secret
metadata:
  name: additional-scrape-configs
  namespace: monitoring
stringData:
  scrape-configs.yaml: |
    - job_name: edera
      metrics_path: /metrics/kubernetes
      kubernetes_sd_configs:
      - role: node
      relabel_configs:
      # Swap the kubelet port (10250) for the Edera metrics port (3035)
      - source_labels: [__address__]
        regex: '(.+):\d+'
        target_label: __address__
        replacement: '${1}:3035'
      # Use the node name as the instance label instead of the raw IP
      - source_labels: [__meta_kubernetes_node_name]
        target_label: instance

Reference the secret from your Prometheus Custom Resource:

apiVersion: monitoring.coreos.com/v1
kind: Prometheus
metadata:
  name: prometheus
  namespace: monitoring
spec:
  additionalScrapeConfigs:
    name: additional-scrape-configs
    key: scrape-configs.yaml
  # ... rest of your Prometheus spec

Verify scraping is working 

# Check the target is up
kubectl port-forward -n monitoring svc/prometheus-operated 9090:9090 &
curl -s 'http://localhost:9090/api/v1/targets' \
  | jq '.data.activeTargets[] | select(.labels.job=="edera") | {health, lastError}'

# Confirm zone metrics are present
curl -s 'http://localhost:9090/api/v1/query?query=zone_cpu_usage_percent' \
  | jq '.data.result | length'

2. Configure the Prometheus Adapter

The adapter translates Prometheus metrics into the Kubernetes custom metrics API so HPAs can consume them. Because Edera zone metrics already carry namespace and pod labels, they map directly to Kubernetes pod resources.

# prometheus-adapter-values.yaml
prometheus:
  url: http://prometheus.monitoring.svc.cluster.local
  port: 9090

rules:
  default: false

  custom:
  - seriesQuery: 'zone_cpu_usage_percent{namespace!="",pod!=""}'
    resources:
      overrides:
        namespace:
          resource: namespace
        pod:
          resource: pod
    name:
      as: zone_cpu_usage_percent
    metricsQuery: 'avg by (namespace, pod) (zone_cpu_usage_percent{<<.LabelMatchers>>})'

Install or upgrade the adapter:

helm upgrade --install prometheus-adapter prometheus-community/prometheus-adapter \
  --namespace monitoring \
  -f prometheus-adapter-values.yaml

Verify the metric is available 

# Should list zone_cpu_usage_percent
kubectl get --raw /apis/custom.metrics.k8s.io/v1beta1 | jq '[.resources[].name]'

# Should return a value per pod
kubectl get --raw \
  "/apis/custom.metrics.k8s.io/v1beta1/namespaces/default/pods/*/zone_cpu_usage_percent" \
  | jq '.items[] | {pod: .describedObject.name, value}'

3. Create a Horizontal Pod Autoscaler (HPA)

With the metric available in the custom metrics API, create an HPA that scales on average zone CPU usage across pods:

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-edera-app
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-edera-app
  minReplicas: 1
  maxReplicas: 10
  metrics:
  - type: Pods
    pods:
      metric:
        name: zone_cpu_usage_percent
      target:
        type: AverageValue
        averageValue: "70"   # scale up when average vCPU usage exceeds 70%

Verify the HPA is working 

# Check HPA status and current metric value
kubectl get hpa my-edera-app

# Watch scaling events
kubectl describe hpa my-edera-app

The TARGETS column in kubectl get hpa shows the current metric value against the target. If it reads <unknown>, the adapter is not reaching the metric – recheck the adapter config and confirm the metric is present in the custom metrics API.

Next steps

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